Kinetics of hepatic transport and factors affecting that transport of organic anions, e.g. bilirubin, BSP and bile salts, are being studied in normal animals (rats, dog, pony and sheep) and mutant Southdown and mutant Corriedale sheep with specific congenital hepatic dysfunctions. Analytical models and transport mechanisms are being tested to provide insight into hepatic function and to provide tools for studying hepatic dysfunction.